Metal cleaning and phosphating composition



2 5 2 1 4 6 mass REFERENCE EXAMINER ar- (WWQ C. W. SMITH METAL CLEANING AND PHOSPHATING COMPOSITION Filed Sept. 16. 1957 ROCARBON NT l 90 6O 7O 6O 5O 4O 3O 20 IO DETERGENT WATER,

LUS ACID, E LSI FIER PHOSPHATE.

/N van: roR C HESTER W 5mm H0 H5 5HE/e/0 4/v 14 TTORNEVS United States Patent METAL CLEANING AND PHOSPHATING COMPOSITION Chester W. Smith, Wayne County, Mich.

. Application September 16, 1957, Serial No. 684,287

20 Claims. (Cl. 1486.15)

This invention relates to the cleaning, phosphating and passivating of metal parts and is a continuation-in-part of my prior filed applications Serial No. 328,795, filed December 30, 1952, now abandoned, and Serial No. 496,927, filed March 27, 1955, now abandoned.

In many metal fabricating industries it is desirable to clean heavy grease, tar, drawing compounds, metallic oxides, and the like from metal parts and to apply a protective rust resistant phosphate coating to the parts preparatory to painting or other operations. Heretofore the cleaning and phosphating has necessitated two major operations comprising first cleaning and rinsing the parts, then the phosphating. The great demand by industry for a stable solution which would reduce the above two operations to a single process has long occupied the research facilities of the major chemical companies supplying metal phosphating and cleaning solutions. All attempts heretofore to combine the hydrocarbon solvent and the phosphating reagents satisfactorily in a single formulation have, however, resulted in an unstable solution from which the water miscible and oil soluble compo nents would separate into two distinct layers or form a typical emulsion. Often a third layer would form containing some of the emulsifier ingredients. In consequence the cleaning actions of such formulations have been erratic and unsatisfactory.

A number of liquid preparations are available which combine a light cleaning action with a phosphating action. Such preparations commonly comprise minor proportions of a detergent or a water miscible solvent such as an alcohol or glycol. Such liquids are satisfactorily employed for phosphating metal parts which are not heavily soiled and usually depend upon application at elevated temperature and brushing or scrubbing for the removal of even light oil films. These preparations are in fact not intended primarily for cleaning, the detergent or solvent being added to assure that the acid phosphating reagents will penetrate to and wet the metal surface to be phosphated.

Attempts to provide homogeneous solutions for both cleaning and phosphating in a single operation have involved the use of major quantities of alcohols, often including minor proportions of the hydrocarbon solvent and still lesser proportions of the phosphating ingredients. Such preparations are inherently unsatisfactory because of the large quantity of alcohol solvent required in comparison to the quantity of water that can be feasibly brought into stable solution with the hydrocarbon solvent. Not only does the high alcohol content constitute a serious fire hazard but the phosphoric acid concentration in the resulting proportionate low water content is usually too strong for the proper phosphating action and unduly etches the metal parts under treatment. Furthermore the solubilizing effect of the high alcohol content is readily upset by evaporation of the alcohol, rendering the solution unstable. Attempts heretofore to reduce the high alcohol content have resulted in separation of the water soluble ingredients from the hydrocarbon solvents,

Patented May 12, 1959 particularly at the elevated temperature usually required for heavy cleaning.

An important object of the present invention is to provide a clear to opalescent, non-toxic liquid preparation of improved stability and effectiveness for simultaneously cleaning metallic parts and applying a protective rust resistant metallic phosphate coating thereto, the preparation being particularly effective at room temperatures for cleaning heavy oils, greases and tarry deposits, metallic oxides, drawing and lapping compounds, and like soils with a minimum of brushing and being adapted to be efiectively applied simply by spraying the preparation on the parts to be treated, or by dipping the parts into the preparation, and thereafter rinsing the parts in a stream of clear cold water.

Another object is to provide a stable liquid preparation of the foregoing character which does not depend upon a preponderance of alcohol or other volatile solvents for its stability and which is readily miscible in cold water at ordinary faucet temperatures approximately 40 F. and is susceptible to being rinsed cleanly from the treated part in a stream of cold water.

Another object of the invention is to provide in the presence of a hydrocarbon solvent a composition with a sufliciently high proportion of water to serve as a vehicle for a relative large quantity of phosphoric acid at a relatively low concentration as compared with prior compositions where the minor proportions of water forced one to compromise between an aqueous phosphoric acid solution which had a sufficient quantity of acid for complete reaction with the metal but too high a concentration and, on the other hand, an aqueous phosphoric acid solution which had the right concentration of acid for a controlled reaction but an insuflicient quantity for complete reaction.

Another object is to provide a stable preparation of the foregoing character containing a chromate rust inhibitor, whereby oxidation of the iron phosphate coating on the treated part from ferrous to ferric phosphate is facilitated to assure a more durable and satisfactory phosphate coating and whereby rusting of the treated steel parts while drying is retarded.

I have now found that the foregoing and related objects can be secured in a composition comprising essentiallyabout 50-80 percent of an aqueous acidic phosphating solution of pH of about 2-3 and free phosphoric acid of about 0.3-0.6 percent by weight of the total preparation; about 430 percent of a hydrocarbon solvent for grease and oil; about 10-30 total percent of an emulsifier and an ethylene oxide condensation detergent; wherein said hydrocarbon solvent has an initial boiling point of about 200-1;150 F. and a final boiling point below about 700 A major difliculty in the formulation of a solution of the character described has been the successful combination of the detergent, solvent, and emulsifier with the desired quantity of the aqueous phosphating solution. For efiicient phosphating, a pH range between 2 and 3 and preferably approximately 2.5 is desired in a solution containing not less than approximately .3% and up to .6% free phosphoric acid by weight of the total preparation. The providing of a sufiicient quantity of phosphate ions for an effective phosphating capacity without exceeding the foregoing requirements requires a major proportion of water in the composition.

It is usually desirable to increase the concentration of phosphate ions above that supplied by phosphoric acid at a suitable pH. This can be done by adding a soluble phosphate such as an alkali metal phosphate. For example about 2 parts by weight of tetra sodium pyrophosphate for each 3 parts by weight of phosphoric acid is a particularly effective proportion. Smaller quantities of phosphate reduce the efiiciency of the phosphating reaction but phosphoric acid alone can carry out the phosphating reaction.

The detergents used in the compositions of the invention are the non-ionic detergents of the class wherein ethylene oxide is reacted wiih relatively high molecular weight acids, alcohols, and mercaptans. These are well known in the detergent art and may be referred to herein generally as ethylene oxide condensation detergents.

One such group of ethylene oxide condensation detergents comprise polyoxyethylene esters empirically identified as follows:

where R is a high molecular weight alkyl having 11 to 19 carbon atoms, such as the alkyl portion of a fatty or rosin acid, and n ranges from 7 to 13. An economically feasible detergent in the last named category which is particularly suitable is the tall oil condensation product of ethylene oxide having a molecular weight of approximately 750. It is to be understood that tall oil is cited merely by way of example and that there are many other sources of the alkyl within the molecular range specified. Specifically, any of the predominant fatty acids in tall oil can be used.

Another group of ethylene oxide condensation detergents are variously known as alkyl aryl polyethylene oxides, alkyl aryl polyethylene glycol alcohols, or alkyl aryl polyethylene glycol ethers empirically identified as follows:

where R is an alkyl having 9-14 carbon atoms, n ranges from 7-14, and the molecular weight ranges from 400 to 800.

The condensation product of ethylene oxide and mercaptans such as tertiary dodecyl mercaptan, having preferably 9 mols of ethylene oxide per mol of tertiary dodecyl mercaptan is an example of an ethylene oxide condensation detergent which gives excellent results. Although the optimum molecular weight for the mercaptan condensation product is approximately 600, the molecular weight can range feasibly from 465 to 730. Another example of a suitable ethylene oxide condensation detergent is tn'methylnonyl polyethylene oxide having preferably 9 mols of ethylene oxide in the polyethylene oxide portion.

The emulsifying agent can comprise a water soluble amine or alkali metal saponified fatty acid, such as potassium tall oil soap; the sodium and potassium salts of oleic, palmitic, or stearic acid; or the like; and will preferably amount to between approximately 2 to parts by weight in Example 1. These emulsifiers are referred to herein as alkali metal soaps. Although this total quantity of emulsifier could be more than doubled without impairing the stability of the formulation, approximately 3 parts have been found satisfactory for phosphating and gleaning with the amount of hydrocarbon solvent speci- Although I prefer an alkali metal soap as the emulsifier the invention can use any of the known emulsifiers of the art, employed individually or in combinations, such as petroleum sulfonate, alkyl sulfate or sulfonate, esters of'alkali metal neutralized sulfosuccinate, or such emulsifiers as represented by the following formulae wherein R represents an alkyl group and x ranges from 5 to 50:

RC0O(CH CH 0),,H (fatty acid esters) RCON(CH CH O) H (fatty acid amides) RN(CH CH O) H, (tertiary amines) The preferred solvents for grease, heavy oil, tarry residues, and the like in the compositions of the inven- .4 tion are all water immiscible and will readily dissolve these substances at normal room temperature. Chlorinated solvents of the foregoing character can be used in a closed system but are objectionably toxic in open systems. hydroca n solvent is accordin lypreferred, whfiammfifi lenm mmw nun- 1 118)? i are s lss vii g smhes The initial uamfi pohts of'such solvents which can bEfsafely and effectively handled range from about 200 F. to about 450 F. and the final boiling point is below about 700 F. For most satisfactory solvent action I prefer hydrocarbon solvents of which at least boil in the 300- 350 F. range.

In preparing the present invention, the aqueous acid phosphating reagents, emulsifier, and detergent are first mixed in the approximate proportions set forth. Thereafter, unless the quantity of solvent required has been previously determined, this quantity can be determined in a trial batch by adding the solvent slowly with constant agitation of the mixture until a clear stable homogeneous solution or liquid is formed. If desired, additional solvent can be added with stirring until cloudiness is first noted.

A small quantity of a chromium ion in the formulation is important as a passivator to 1 it rusting of the treated steel parts, particularly if the parts are not dried quickly, and to accelerate oxidation of the phosphate coating from ferrous to ferric phosphate, thereby to effect a superior protective coating. Heretofore the chromium ion has not been added to a stable phosphating and cleaning solution, so that an additional operation of spraying with a rust inhibiting chromate solution has been necessary after the phosphating operation. In the present instance, although the chromium ion is not critical to the stability of the solution, the chromium ion in the proportion specified does not render the solution unstable. Accordingly the present invention permits combining the three operations of cleaning, phosphating, and passivating in a single operation.

The chromium ion may be a chromate or dichrom or may be added as the trivalent ion as in chromium chloridg The chromium compound may be added in a range of about .0l% to about 0.1%. Although sodium dichromate is preferred for the source of the chromate radical in the cleaning and phosphating solution concerned herein, corresponding amounts of the chromium ion can be supplied from other sources, such as chromic acid, other alkali metal dichromates or chromates, trivalent chromium salts such as chromium chloride, and the like. The term compounds providing an ion from the class consisting of chromium and chromate includes all such sources.

I have also found that the passivating action of chromium ion can be en hgnced mm A soluble moylbdenum compound can be added m a variety of forms such as molybdie oxide, sodium moylbd3t e and the like. The use of mo ybdenum in the compositions of the invention yield a heavier phosphate coatmg of greater corrosion resistance. The resulting coating is particularly resistant to flash rusting. The coating is also more uniform and of a beautiful blue color.

The molybdenum compound is best used in a proportion of about 0.02-0.2 percent by weight but the limits are not critical. In general best results are secured when the molybdenum compound is used in about double the proportion of the chromium compound.

The above composition may also be defined as:

Aqueous acidic phosphate solution 63 Hydrocarbon solvent 21 Detergent plus emulsifier 16 Chromium ion 0.05

Since the above proportions add up to 100 parts by weight the numbers may also be considered as weight percent and the term percent as used herein is intended to mean weight percent."

The composition of Example 1 was found to be clear, homogeneous and stable. Upon being applied to a steel surface it simultaneously removed the grease and soil from the surface, evenly phosphated the surface, and

' The above composition, when mixed, was found to be clean, homogeneous and stable. Upon being applied to steel surfaces it simultaneously removed the grease and grime therefrom and evenly phosphated the treated surface.

Example 3 Ingredients: Parts by weight Phosphoric acid 3 Trisodium phosphate 1 Tall oil-ethylene oxide condensation detergent- 8 Petroleum sulfonate 4 Hydrocarbon 14 g ornate 0.08 Molybdenum oxide 0.18 Water 70 The above composition may also be defined as:

Ingredients: Parts by weight Aqueous acidic phosphate solution 74 Hydrocarbon solvent 14 Detergent plus emulsifier 12 Chromium ion 0.08 Molybdenum compound 0.16

The above composition, when mixed, was found to be clear, homogeneous and stable. Upon being tested on steel surfaces it simultaneously cleaned the metals, phosphated them, and passivated them.

The above examples were repeated using a wide variety of ethylene oxide condensation detergents, emulsifiers and hydrocarbons in a wide variety of proportions in acidic aqueous phosphate solutions. Many of these were clear to opalescent, homogeneous, and stable and others were not. By plotting these compositions on a ternary diagram I found the satisfactory compositions could be clearly defined.

In this connection the accompanying drawing is a ternary diagram whose coordinates are in weight percent: hydrocarbon solvent; water plus acid and phosphate; and detergent plus emulsifier.

The solid line encloses the area of those compositions which meet the objectives of the present invention. The dotted line encloses an area of approximately clear compositions.

I claim:

1. An opalescent to clear, stable liquid composition for simultaneously cleaning and phosphating metal surfaces consisting essentially of about 50-80 percent of an aqueous acidic phosphating solution; about 4-30 percent of a hydrocarbon solvent for grease and oil; and about 10-30 total percent of an emulsifier and an ethylene oxide condensation detergent, wherein said hydrocarbon solventhas an initial boiling point of about 200-450 F. and a final boiling point below about 700 F.

2. An opalescent to clear, stable liquid composition for simultaneously cleaning, phosphating and passivating metal surfaces consisting essentially of about 50-80 percent of an aqueous acidic phosphating solution; about 4-30 percent hydrocarbon solvent for grease and oil; about 0.01-0.1 percent sodium dichromate; and about 10-30 total percent of an emulsifier and an ethylene oxide condensation detergent, wherein said hydrocarbon solvent has an initial boiling point of about 200-450 F. and a final boiling point below about 700 F.

3. An opalescent to clear, stable liquid composition for simultaneously cleaning and phosphating metal surfaces consisting essentially of about 50-80 percent of an aqueous acidic phosphating solution; about 4-30 percent hydrocarbon solvent for grease and oil; about 2-5 percent of an emulsifier and about 5-28 percent of an ethylene oxide condensation detergent wherein said hydrocarbon solvent has an initial boiling point of about 200- 450 F. and a final boiling point below about 700 F.

4. The composition according to claim 1 wherein the detergent is a polyoxyethylene ester.

5. An opalescent to clear, stable liquid composition for simultaneously cleaning and phosphating metal surfaces comprising essentially about 50-80 percent of an acidic aqueous phosphate solution at a pH of about 2-3; about 4-30 percent of a hydrocarbon solvent for grease and oil; and about 10-30 total percent of an emulsifier and an ethylene oxide condensation detergent, wherein said hydrocarbon solvent has an initial boiling point of about 200-450 F. and a final boiling point below about 700 F.

6. An opalescent to clear, stable liquid composition for simultaneously cleaning and phosphating metal surfaces comprising essentially about 50-80 percent of an acidic aqueous phosphate solution having free phosphoric acid in a proportion of about 0.3-0.6 percent by weight of the total composition; about 4-30 percent of a hydrocarbon solvent for grease and oil; and about 10-30 total percent of an emulsifier and an ethylene oxide condensation detergent, wherein said hydrocarbon solvent has an initial boiling point of about 200-450 F. and a final boiling point below about 700 F.

7. An opalescent to clear, stable liquid composition for simultaneously cleaning and phosphating metal surfaces comprising essentially about 50-80 percent of an acidic aqueous phosphate solution in which about 3 such percent are anhydrous phosphoric acid and about 2 such percent are an alkali metal phosphate; about 4-30 percent of a hydrocarbon solvent for grease and oil; and about 10-30 total percent of an emulsifier and an ethylene oxide condensation detergent, wherein said hydrocarbon solvent has an initial boiling point of about 200-450 F. and a final boiling point below about 700 F.

8. An opalescent to clear, stable liquid composition for simultaneously cleaning, phosphating, and passivating metal surfaces comprising essentially about 50-80 percent of an acidic aqueous phosphate solution at a pH of about 2-3; about 4-30 percent of a hydrocarbon solvent for grease and oil; about 0.01-0.1 percent of a compound providing an ion from the class consisting of chromium and chromate; and about 10-30 total percent of an emulsifier and an ethylene oxide condensation detergent, wherein said hydrocarbon solvent has an initial boiling point of about 200-450 F. and a final boiling point below about 700 F.

9. An opalescent to clear, stable liquid composition for simultaneously cleaning, phosphating, and passivating metal surfaces comprising essentially about 50-80 percent of an acidic aqueous phosphate solution having free phosphoric acid in a proportion of about 0.3-0.6 percent by weight of the total composition; about 4-30 percent hydrocarbon solvent for grease and oil; about 0.01-0.1 percent of a compound providing an ion from the class consisting of chromium and chromate; and about 10-30 total percent of an emulsifier and an ethylene oxide condensation detergent, wherein said hydrocarbon solvent has an initial boiling point of about 200450 F. and a final boiling point below about 700 F.

10. An opalescent to clear, stable liquid composition for simultaneously cleaning, phosphating, and passivating metal surfaces comprising essentially about 50-80 percent of an acidic aqueous phosphate solution in which about 3 such percent are anhydrous phosphoric acid and about 2 such percent are an alkali metal phosphate; about 4-30 percent of a hydrocarbon solvent about 2-5 percent of an emulsifier; about -28 percent of an ethylene oxide condensation detergent; and about 0.05 percent of an alkali metal chromate; wherein said hydrocarbon solvent has an initial boiling point of about 200450 F. and a final boiling point below about 700 F.

11. In a method for cleaning oily deposits from a metal surface and simultaneously applying a phosphate coating to said surface, the steps of treating said surface with the composition of claim 1 and thereafter rinsing said surface with water.

12. In a method for cleaning oily deposits from a metal surface, simultaneously applying a phosphate coating to said surface and simultaneously passivating said surface, the steps of treating said surface with the composition of claim 2 and thereafter rinsing said surface with water.

13. In a method for cleaning oily deposits from a metal surface and simultaneously applying a phosphate coating to said surface, the steps of treating said surface with the composition of claim 3 and thereafter rinsing said surface with water.

14. In a method for cleaning oily deposits from a metal surface and simultaneously applying a phosphate coating to said surface, the steps of treating said surface with the composition of claim 4 and thereafter rinsing said surface with water.

15. In a method for cleaning oily deposits from a metal surface and simultaneously applying a phosphate coating to said surface, the steps of treating said surface with the composition of claim 5 and thereafter rinsing said surface with water.

16. In a method for cleaning oily deposits from a metal surface and simultaneously applying a phosphate coating to said surface, the steps of treating said surface with the composition of claim 6 and thereafter rinsing said surface with water.

17. In a method for cleaning oily deposits from a metal surface and simultaneously applying a phosphate coating to said surface, the steps of treating said surface with the composition of claim 7 and thereafter rinsing said surface with water.

18. In a method for cleaning oily deposits from a metal surface, simultaneously applying a phosphate coating to said surface, and simultaneously passivating said surface, the steps of treating said surface with the composition of claim 8 and thereafter rinsing said surface with water.

19. An opalescent to clear, stable liquid composition for simultaneously cleaning, phosphating and passivating metal surfaces consisting essentially of about -80 percent of an aqueous acidic phosphating solution; about 4-30 percent hydrocarbon solvent for grease and oil; about 0.01-0.1 percent of a compound providing an ion from the class consisting of chromium and chromate; about 0.02-0.2 percent of a soluble molybdenum compound; and about 10-30 total percent of an emulsifier and an ethylene oxide condensation detergent; wherein said hydrocarbon solvent has an initial boiling point below about 200-450 F. and a final boiling point below about 700 F.

20. In a method for cleaning oily deposits from a metal surface, simultaneously applying a phosphate coating to said surface and simultaneously passivating said surface, the steps of treating said surface with the composition of claim 19 and thereafter rinsing said surface with water.

References Cited in the file of this patent UNITED STATES PATENTS 2,396,776 Douty et al. Mar. 19, 1946 2,479,423 Snyder Aug. 16, 1949 2,744,555 Nicholson May 8, 1956 2,809,906 Baecker et al Oct. 15, 1957 FOREIGN PATENTS 473,408 Canada May 8, 1951 1,062,140 France Dec. 2, 1953 717,866 Great Britain Nov. 3, 1954 

1. AN OPALESCENT TO CLEAR, STABLE LIQUID COMPOSITION FOR SIMULTANEOUSLY CLEANING AND PHOSHATING METAL SURFACE CONSISTING ESSENTIALLY OF ABOUT 50-80 PERCENT OF AN AQUEOUS ACIDIC PHOSPHATING SOLUTION; ABOUT 4-30 PERCENT OF A HYDROCARBON SOLVENT FOR GREASE AND OIL; AND ABOUT 10-30 TOTAL PERCENT OF AN EMULSIFIER AND AN ETHYLENE OXIDE CONDENSATION DETERGENT, WHEREIN SAID HYDROCARBON SOLVENT HAS AN INITIAL BOILING POINT OF ABOUT 200*-450* F. AND A FINAL BOILING POINT BELOW ABOUT 700* F. 